Dozens of trailers filled with parcels and packages were awaiting processing at the agency’s three biggest hubs as Canada Post employees from several Quebec communities joined countrywide rotating strikes a day after about 6,000 workers walked off the job in Montreal.

“At this point there is a backlog of over 150 trailers in Toronto, Vancouver and Montreal of items waiting to be unloaded and processed, with more arriving every day,” said Canada Post spokesman Jon Hamilton.

“Once processed, these items have to be delivered without overburdening our delivery employees. As a result, customers could see delays of several days.”

Combined, the three key locations can process a million parcels a day from across the country, Hamilton said.

The Canadian Union of Postal Workers said walkouts started this morning in Saint-Jerome, Vaudreuil-Dorion, Sorel, Sainte-Therese de Blainville and Valleyfield in Quebec.

Workers in Joliette, Que., have been on strike since 1 a.m. EDT, and the Prince Edward Island communities of Summerside and Charlottetown were hit by strikes that started at midnight local time.

The Montreal walkout ended Tuesday night, but another 16 communities across the country are now taking part in the 24-hour strikes, the union said.

In Ontario, walkouts began in Arnprior-Renfrew and Ottawa Wednesday morning, but strikes in Fort Frances, Deep River and other communities in the province ended.

Postal workers also walked off the job at four locals on Vancouver Island.

Meanwhile, employees in the Saskatchewan communities of Saskatoon, Weyburn and Moose Jaw are no longer on strike.

The union and the postal service have been unable to reach new collective agreements for two bargaining units after 10 months of negotiations.

Canada Post has said it provided “significant” offers to its employees, including wage hikes.

“But they don’t address a single one of our major issues, CUPW national president Mike Palecek said Wednesday in a statement on the union’s website.